A. Field of the Invention
The present invention relates to a paper feed mechanism of a printer, or more particularly, to a mechanism for exactly transmitting a rotative force of a drive shaft which interlocks a drive mechanism without play to a sprocket wheel for feeding a printing paper and for locating and detaining the sprocket wheel at a desired position by an easy operation.
B. Description of the Prior Art
As the processing speed in a central processing device of an electric computer has been increased, a high-speed printer has been correspondingly required, and a dot printer is put in use. For example, the dot printer represents a character on by dots such as a 7.times.9 dot configuration, and printing is carried out in such a manner that a printing paper which has sprocket holes is fed by a paper feed mechanism to a dot printing mechanism which is arranged at a right angle to the direction of the printing paper. The above-said paper feed mechanism has to exactly feed the printing paper to prevent an unevenness of pitch of dots which form a character and has to be easily operated when the printing paper is set.
In the prior art paper feed mechanism, there is play between the sprocket wheel which feeds the printing paper and the drive shaft for driving the sprocket wheel, therefore, the feeding of printing paper becomes unexact to cause an unevenness of pitch of dots, or in case of a matrix printer, an unevenness of a line feed pitch, and the printing quality is deteriorated. In addition, when the sprocket wheel is traversed in accordance with the width of the printing paper, the paper feed mechanism has difficulty handling this because the detaining mechanism comprises a screw.